In a shingled magnetic recording (SMR) magnetic disk device (hereinafter, an SMR device), a sector position of a sector that is a write-retrying target is different from the sector position of the sector in which the write-retrying is actually performed. That is, a sector in which a writing error occurs is handled as a defective sector during the writing-retrying and the data to be written to that defective sector are instead written to the sector following the defective sector. In this way, the write re-trying process is not performed on the defective sector, and therefore cannot adversely affect adjacent tracks due to data being written multiple times in the same location.
On the other hand, in SMR devices, an error correction process for an entire track is generally employed as an error correction method. To enable the error correction process for an entire track, an exclusive OR (XOR) operation is performed on write data to generate parity information for the track, starting from a head or first sector of the track. The parity information for the track is then recorded in a predetermined sector of the track. Thus, the error correction process for a track depends on generating a so-called parity sector for that track.
In practice, in the error correction process for a specific track, the write data is mixed with a different seed value for each of the sectors, so that the parity information is not biased to I/O. In this case, a physical sector number is generally set as such a seed value for mixing. However, in an SMR device, a position of the sector on a medium is changed by the write-retrying process, so that the seed value for mixing is different for the sector in which the write-retrying is actually performed than the seed value for mixing for the original sector (where the original sector is the target sector of the write-retrying process). Thus, for the same data, the parity information has a different value. For this reason, when a writing error occurs, the parity sector for a particular track needs to be calculated starting at the head or first sector of the track.